Unbalanced
Fault Analysis Problem Formulation
A 30 MVA,
13.2KV synchronous generator has a solidly grounded neutral. Its positive,
negative and zero sequence impedances are 0.30, 0.40 and 0.05 p.u respectively.
Determine the following:
a)
What value of reactance must be placed in the
generator neutral so that the fault current for a line to ground fault of zero
fault impedance shall not exceed the rated line current?
b)
What value of resistance in the neutral will serve
the same purpose?
c)
What value of reactance must be placed in the
neutral of the generator to restrict the fault current to ground to rated line
current for a double line to ground fault?
d)
What will be the magnitudes of the line currents
when the ground current is restricted as above?
e)
As the reactance in the neutral is indefinitely
increased, what are the limiting values of the line currents?
Two
alternators are operating in parallel and supplying a synchronous motor which
is receiving 60MW power at 0.8 power factor lagging at 6.0 KV. Single line
diagram for this system is given in fig. Data are given below. Compute the
fault current when a single line to ground fault occurs at the middle of the
line through a fault resistance of 4.033 ohm.
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